Atomic layer deposition (ALD) and chemical vapor deposition (CVD) are two exemplary methods used in semiconductor fabrication to deposit thin films on a substrate in a processing chamber. Typical processing chambers may include a substrate support, for example a heater plate, which often includes a sealing ring positioned around perimeter. The substrate often rests upon a portion of the sealing ring as well as support elements inside of the sealing ring. The sealing ring may also provide a seal with the backside of the substrate to allow the formation of a backside pressure. The seal may also minimize contamination of the backside of the substrate by process gases. However, the inventors have observed several problems with convention sealing rings.
For example, contact between the substrate and metallic components during processing often leads to metal contamination of the substrate and a high instance of product failure. To alleviate the contamination, substrate support rings formed from metallic materials may be coated with a non-metallic material to eliminate, or at least reduce, metallic contact with the substrate. Alternatively, support rings may be formed from non-metallic materials to prevent direct metal contamination.
In addition, semiconductor fabrication often takes place at elevated temperatures, which can cause thermal expansion of the substrate support and the sealing ring. Differing thermal expansion characteristics of components of the substrate support can cause processing difficulties. For example, when using a metallic sealing ring having a non-metallic coating, the ring material and the coating typically have different thermal expansion characteristics, causing flaking and failure of the coating. Also, non-metallic sealing rings often have thermal expansion characteristics that differ from the substrate support plate to which they are mounted, leading to warping or cracking of the ring during processing.
Lastly, the inventors have observed that during processing, a portion of the substrate resting upon the sealing ring may be adversely affected by the higher thermal conductivity of the sealing ring as compared to regions of the substrate not supported by the sealing ring.
Therefore, the inventors have provided embodiments of improved substrate supports.